Applied are such analytical methods as macroscopic morphology inspection, physical-chemical  performance test, scanning electron microscope and energy spectrum analysis to analyze and investigate reasons for the failure of a subsea pipeline. Results show that corrosion products in inter wall of bend consist mainly of FeCO₃ and Fe₃O₄ and corrosion products in outer wall of bend consist mainly of FeCO₃ and FeOOH. Water media containing corrosive gas and high pressure points are mainly distributed in outer side of bend, which leads to more severe corrosion environment than inner.side of bend and corrosion tendency in outer side is stronger than the inner side, prone to corrosion perforation. Before perforation, outer arc side of bend suffers from carbon dioxide corrosion in most cases and perforation extends from internal wall to external wall and after perforation, inner and outer walls of bend suffer from carbon dioxide and oxygen corrosion at the same time.